Circular stapling device including buttress material

ABSTRACT

An anvil assembly includes a circular anvil head that supports a crush ring, an anvil cap that supports an o-ring, and a circular anvil buttress member. The cap connects to the head and is movable relative to the head between approximated and unapproximated positions. The crush ring is spaced from the cap when the cap is in the approximated position and movable into engagement with the cap to move the cap to the unapproximated position. The buttress member includes a body portion and an extension portion. The body portion is supported on the head and the extension portion is secureable between the o-ring and the head when the cap is in the approximated position. The extension portion is releasable from between the o-ring and the head when the cap is disposed in the unapproximated position so that the body portion separates from the head.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/875,419, filed Jan. 19, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/924,202, filed Oct. 27, 2015, now U.S. Pat. No.9,895,151, which is a continuation of U.S. patent application Ser. No.13/758,100, filed Feb. 4, 2013, now U.S. Pat. No. 9,192,383, the entiredisclosure of each of which is hereby incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to surgical stapling devices and, moreparticularly, to structures and methods for removably attaching buttressmaterial to circular surgical stapling devices for use in anastomosisprocedures.

BACKGROUND

Fasteners have been used to replace suturing when joining various bodystructures such as, for example, the bowel or bronchus. Surgicalstapling devices employed to apply these fasteners are generallydesigned to simultaneously cut and seal tissue to reduce the time andrisks involved with anastomosis procedures.

Circular surgical stapling devices are employed by surgeons tosequentially or simultaneously apply one or more surgical fasteners,e.g., staples or two-part fasteners, to body tissue for the purpose ofjoining segments of body tissue together and/or for the creation ofanastomoses. Circular surgical stapling devices generally include anannular fastener cartridge assembly that supports a plurality of annularrows of fasteners, an annular anvil assembly operatively associated withthe fastener cartridge assembly which provides a surface against whichthe fasteners are formed upon a firing of the circular stapling device,and an annular blade for cutting tissue.

For most procedures, the use of bare fasteners, with the fasteners indirect contact with the patient's tissue, is generally acceptable. Theintegrity of the tissue will normally serve to prevent the fastenersfrom tearing out of the tissue and compromising the sealing beforehealing has occurred. However, in some surgical operations buttressmaterials are employed by surgeons in combination with circular staplingdevices to bridge, repair and/or reinforce tissue defects within apatient. In particular, buttress materials reduce the trauma suffered bythe patient, reduce the instances of leakage, reduce the instances ofbleeding, and create a relatively strong bond between adjacent bodytissues.

Accordingly, there is a need for reliably and removably attachingbuttress material onto a circular stapling device so that the buttressmaterial does not interfere with the operation of the device, remains onthe device until after the fasteners are fired, and is convenient andeasy to install and use.

SUMMARY

According to one aspect, a circular stapling device includes a handleassembly, an elongate body that extends from the handle assembly, and anend effector mounted on a distal end of the elongate body and includinga cartridge assembly and an anvil assembly.

The anvil assembly includes a circular anvil head that supports a crushring, an anvil cap that supports an o-ring, and a circular anvilbuttress member. In embodiments, the o-ring is formed of an elastomericmaterial including nitrile.

The anvil cap connects to the anvil head and is movable relative to theanvil head between an approximated position and an unapproximatedposition. The crush ring is spaced from the anvil cap when the anvil capis disposed in the approximated position and movable into engagementwith the anvil cap to move the anvil cap to the unapproximated position.The anvil cap defines a groove in a bottom surface of the anvil cap andthe o-ring is secured within the groove. The o-ring is disposed in acompressed condition when the anvil cap is disposed in the approximatedposition and an uncompressed condition when the anvil cap is disposed inthe unapproximated position.

The anvil cap includes a snap feature and the anvil head defines a firstrecess and a second recess. The snap feature is selectively positionablewithin one of the first recess and the second recess. The snap featureis positionable within the first recess when the anvil cap is disposedin the approximated position and is positionable within the secondrecess when the anvil cap is disposed in the unapproximated position.The first recess and the second recess are separated by a rampedpartition. The snap feature cams over the ramped feature as the anvilcap moves from the approximated position to the unapproximated position.The snap feature flexes outwardly from the first recess as the snapfeature cams over the ramped partition and flexes inwardly into thesecond recess after camming over the ramped partition. The snap featuremaintains the anvil cap secured to the anvil head when the snap featureis disposed in the second recess.

The circular anvil buttress member includes a body portion and anextension portion that extends from the body portion. The body portionis supported on a tissue engaging surface of the anvil head. Theextension portion is secureable between the o-ring and the anvil headwhen the anvil cap is disposed in the approximated position. Theextension portion is releasable from between the o-ring and the anvilhead when the anvil cap is disposed in the unapproximated position sothat the body portion separates from the tissue engaging surface of theanvil head. The extension portion includes one or more tabs. The o-ringis compressed against the one or more tabs when the anvil cap isdisposed in the approximated position to maintain the body portionsupported on the tissue engaging surface of the anvil head.

In another aspect, then anvil assembly includes a circular anvil headthat supports a crush ring, and anvil cap that connects to the anvilhead and supports an o-ring, and a circular anvil buttress member.

The anvil cap is movable relative to the anvil head between anapproximated position and an unapproximated position. The crush ring isspaced from the anvil cap when the anvil cap is disposed in theapproximated position and movable into engagement with the anvil cap tomove the anvil cap to the unapproximated position. The anvil cap definesa groove in a bottom surface of the anvil cap. The o-ring is securedwithin the groove. The o-ring is disposed in a compressed condition whenthe anvil cap is disposed in the approximated position and in anuncompressed condition when the anvil cap is disposed in theunapproximated position. In embodiments, the o-ring is formed of anelastomeric material including nitrile.

The anvil cap includes a snap feature and the anvil head defines a firstrecess and a second recess. The snap feature is selectively positionablewithin one of the first recess and the second recess. The snap featureis positionable within the first recess when the anvil cap is disposedin the approximated position and is positionable within the secondrecess when the anvil cap is disposed in the unapproximated position.The first recess and the second recess are separated by a rampedpartition. The snap feature cams over the ramped feature as the anvilcap moves from the approximated position to the unapproximated position.The snap feature flexes outwardly from the first recess as the snapfeature cams over the ramped partition and flexes inwardly into thesecond recess after camming over the ramped partition. The snap featuremaintains the anvil cap secured to the anvil head when the snap featureis disposed in the second recess.

The circular anvil buttress member includes a body portion and anextension portion that extends from the body portion. The body portionis supported on a tissue engaging surface of the anvil head. Theextension portion is secureable between the o-ring and the anvil headwhen the anvil cap is disposed in the approximated position. Theextension portion is releasable from between the o-ring and the anvilhead when the anvil cap is disposed in the unapproximated position sothat the body portion separates from the tissue engaging surface of theanvil head. The extension portion includes one or more tabs. The o-ringis compressed against the one or more tabs when the anvil cap isdisposed in the approximated position to maintain the body portionsupported on the tissue engaging surface of the anvil head.

According to yet another aspect, the present disclosure is directed to amethod for releasing an anvil buttress member from an anvil assembly ofa circular stapling device. The method includes the step of providing acircular stapling device including an elongate member having an endeffector mounted on a distal end of the elongate body. The end effectorincludes an anvil assembly that includes an anvil head and an anvil capthat supports an o-ring. The anvil assembly includes an extensionportion of an anvil buttress member secured between the o-ring and theanvil head so that a body portion of the anvil buttress member issupported on a tissue engaging surface of the anvil head. The methodinvolves moving the o-ring relative to anvil head to release the anvilbuttress member from the anvil assembly. Another step includes moving acrush ring supported on the anvil head into engagement with the anvilcap to move the o-ring relative to the anvil head. Yet another stepinvolves spacing the o-ring and the anvil head relative to one anotherin response to engagement of the crush ring with the anvil head toprovide a gap between the o-ring and the anvil head sufficient to enablethe extension portion of the anvil buttress member to be released frombetween the o-ring and the anvil head.

Other aspects, features, and advantages will be apparent from thedescription, drawings, and claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosureand, together with a general description of the disclosure given aboveand the detailed description given below, serve to explain theprinciples of the disclosure, wherein:

FIG. 1 is a perspective view of a circular surgical stapling deviceaccording to the present disclosure;

FIG. 2 is an enlarged top perspective view of an embodiment of an anvilassembly and a shaft member of the presently disclosed circular surgicalstapling device;

FIG. 3 is a bottom perspective view of the anvil assembly and a portionof the shaft member;

FIG. 4 is a perspective view, with parts separated, of the anvilassembly and the shaft member;

FIGS. 5-6 are progressive cross-sectional views of the anvil assemblyand a distal portion of the shaft member, each view showing the anvilassembly in a different configuration; and

FIG. 7 is a perspective view, with parts separated, of anotherembodiment of an anvil assembly.

DETAILED DESCRIPTION

As used herein, the term “clinician” refers to a doctor, a nurse, or anyother care provider and may include support personnel. Particularembodiments of the present disclosure will be described herein withreference to the accompanying drawings. As shown in the drawings and asdescribed throughout the following description, and as is traditionalwhen referring to relative positioning on an object, the term “proximal”refers to the end of the device that is closer to the clinician and theterm “distal” refers to the end of the device that is farther from theclinician. In the following description, well-known functions orconstructions are not described in detail to avoid obscuring the presentdisclosure in unnecessary detail.

Referring initially to FIG. 1, a circular surgical stapling device foruse with a buttress material is disclosed herein and is generallydesignated as 10. In embodiments, the surgical stapling device 10 isadapted for reuse and, in certain embodiments, the surgical staplingdevice 10 is adapted for a single use and can be disposable.

The circular stapling device 10 includes a handle assembly 20, a tubularelongate body 30, and an end effector 40. The end effector 40 can beprovided as a removable and replaceable assembly. The handle assembly 20includes a rotatable advancing member 22 and a pivotable trigger member24 that are operatively coupled to any number of drivers supported bythe surgical stapling device 10 to effectuate a firing of the surgicalstapling device 10. The elongate body 30 extends distally from a distalend portion of the handle assembly 20 to a proximal end portion of theend effector 40 so that the elongate body 30 is disposed between thehandle assembly 20 and the end effector 40. In some embodiments, theelongate body 30 has a linear shape along the length of the elongatebody 30, and in certain embodiments, the elongate body 30 has a curvedshape along the length of the elongate body 30.

The end effector 40 includes a fastener cartridge assembly 100, an anvilassembly 200, and a shaft 300. The shaft 300 includes a proximal endportion that is secured to the fastener cartridge assembly 100 and adistal end portion that is secured to the anvil assembly 200. Inembodiments, the fastener cartridge assembly 100 and/or the anvilassembly 200 may be replaced and the circular stapling device 10 may bereused. In embodiments, the end effector 40 supports a knife assemblywith a substantially cylindrical knife 400 (FIG. 6) adapted to cuttissue.

Reference may be made to U.S. Pat. No. 5,915,616 to Viola et al. andcommonly owned U.S. Patent Application Publication No. 2011/0174099, theentire contents of which are incorporated herein by reference, for adetailed discussion of the construction and operation of exemplarycircular stapling devices.

Turning now to FIGS. 2-6, the anvil assembly 200 includes a circularanvil head 210, an o-ring 215, an anvil cap 220, a circular anvilbuttress member 230, a crush ring member 240, an anvil plate 250, and aring assembly 260.

With continued reference to FIG. 4, the circular anvil head 210 includesa head body 212 that supports the crush ring member 240, the ringassembly 260, and the anvil plate 250. The head body 212 has a connector214 that extends proximally from the head body 212 and is dimensioned tooperatively couple to a distal end portion 302 of the shaft 300. Theconnector 214 defines a pair of opposed channels 214 a. One or moreengaging passages 216 are defined by the head body 212 and extendthrough the head body 212. As shown in FIGS. 5-6, a distal surface ofthe head body 212 includes one or more ramped partitions 218 thatseparate a first recess 218 a and a second recess 218 b defined onopposite sides of the ramped partition 218.

Referring again to FIG. 4, the anvil cap 220 includes a cap body 222that is supported on the distal surface of the anvil head 210 so thatthe o-ring 215 is positionable between the cap body 222 and the anvilhead 210. In particular, the cap body 222 defines an annular groove 222a within which the o-ring 215 is dimensioned to be received. The capbody 222 includes one or more engaging features 224 and one or more snapfeatures 226 that extend proximally from the cap body 222. Referringalso to FIGS. 5-6, the snap feature 226 includes a tooth 226 a thatextends radially inwardly. The first and second recesses 218 a, 218 b ofthe anvil head 210 are each dimensioned to receive the tooth 226 a tofacilitate securement of the anvil cap 220 to the anvil head 210. Thecap body 222 defines an opening 228 dimensioned to enable the snapfeature 226 to flex radially outwardly to permit the anvil cap 220 tomove relative to the anvil head 210 between approximated andunapproximated positions.

The anvil plate 250 secures to the proximal surface of the anvil head210 and has an annular body 252 that defines an opening 254therethrough. The annular body 252 has a tissue engaging surface 256that defines a plurality of fastener forming pockets 256 a. Theplurality of fastener forming pockets 256 a is arranged in an annulararray about the tissue engaging surface 256 of the annular body 252.

The circular anvil buttress member 230 is selectively supported on theanvil plate 250 and has an annular body portion 232 and one or moreextension portions 234 that extends radially from the body portion 232.The body portion 232 is dimensioned to overly the tissue engagingsurface 256 of the anvil plate 250 and defines a central opening 236therethrough. The extension portion 234 includes a plurality of spacedapart tabs 234 a that extend radially outwardly about the body portion232. The plurality of spaced apart tabs 234 a are selectivelypositionable between the proximal surface of the anvil cap 220 and thedistal surface of the anvil head 210 to selectively secure the annularbody portion 232 against the tissue engaging surface 256 of the anvilplate 250 when the anvil cap 220 is disposed in the approximatedposition. As described in greater detail below, the extension portion234 is releasable from the between the anvil cap 220 and the anvil head210 when the anvil cap 220 is moved to the unapproximated position sothat the body portion 232 separates from the tissue engaging surface 256of the anvil plate 250.

The crush ring member 240 is supported on the anvil head 210 andincludes a generally annular body 242 having a plurality of tab members244 that secure to a proximal surface of the anvil head 210 and extendfrom the body 242 at radially spaced locations along an outer surface ofthe body 242. The crush ring member 240 is dimensioned to be spaced fromthe one or more engaging features 224 of the cap body 222 when the anvilcap 220 is disposed in the approximated position and movable intoengagement with the one or more engaging features 224 to move the anvilcap 220 to the unapproximated position. The annular body 242 defines anaperture 246 therethrough that is dimensioned to receive the connector214 of the head body 212 when the crush ring member 240 is secured tothe anvil head 210.

As illustrated in FIG. 4, the ring assembly 260 is supported between theanvil head 210 and the anvil plate 250. The ring assembly 260 includes afirst annular member 270, a second annular member 280, and a thirdannular member 290.

The first annular member 270 includes a body 272 having a proximalsurface 272 a and a distal surface 272 b with a central opening 274defined by an inner surface 272 c that extends between the proximalsurface 272 a and the distal surface 272 b of the body 272. The body 272includes a plurality of annularly spaced apart projections 276 thatextend distally from the distal surface 272 b of the body 272. Eachprojection 276 includes a pair of opposed support arms 276 a that extendfrom the projection 276. The opposed support arms 276 a are disposedsubstantially transverse to the projection 276.

The second annular member 280 includes a body 282 having a proximalsurface 282 a and a distal surface 282 b with a central opening 284defined by an inner surface 282 c that extends between the proximalsurface 282 a and the distal surface 282 b of the body 282. The body 282includes a pair of opposed nubs 286 that extend from the inner surface282 c and are dimensioned to slide within the channels 214 a defined inthe connector 214 of the anvil head 210. The body 282 includes aplurality of ledges 288 extend from an outer surface 282 d of the body282 and radially about the outer surface 282 d of the body 282. Adjacentledges 288 define a passage 285 therebetween that is dimensioned toreceive the projections 276 of the first annular member 270 such thatthe opposed support arms 276 a of the projections 276 are supportedagainst the adjacent ledges 288 on the distal surface 282 b of thesecond annular member 280 when the first and second annular members 270,280 are secured together. The portion of the outer surface 282 d of thebody 282 positioned proximally of the ledges 288 is dimensioned to beseated within the central opening 274 defined by the first annularmember 270 when the first and second annular members 270, 280 aresecured together. As shown in FIGS. 5 and 6, at least portions of theproximal surfaces of the first and second annular members 270, 280 aresubstantially aligned when the first and second annular members 270, 280are secured together.

The third annular member 290 includes a body 292 having a proximalsurface 292 a and a distal surface 292 b with a central opening 294defined by an inner surface 292 c that extends between the proximalsurface 292 a and the distal surface 292 b of the body 292. As shown inFIGS. 5 and 6, when the annular members of the ring assembly 260 aresecured together, the inner surface 292 c of the third annular member290 radially surrounds an outer surface of the ledges 288 of the secondannular member 280 and retains the projections 276 of the first annularmember 270 within the passages 285 of the second annular member 280. Inthis regard, the distal surface 272 b of the first annular member 270engages the proximal surface 292 a of the third annular member 290 andat least portions of the distal surface 292 b of the third annularmember 290 and the distal surface 282 b of the second annular member 280are disposed in substantial alignment and in contact with a proximalsurface of the crush ring 240.

During operation of the surgical stapling device 10, the anvil assembly200 and the cartridge assembly 100 are approximated by the actuation ofadvancing member 22 until the anvil assembly 200 and the cartridgeassembly 100 are suitably clamped against tissue of a patient. Thetrigger member 24 is then actuated to fire the surgical stapling device10. Upon a firing of the surgical stapling device 10, the legs of thefasteners supported within the cartridge assembly 100 are advancedthrough the clamped tissue and any buttress material clamped againsttissue including the anvil buttress member 230 and any buttress materialthat may supported on the cartridge assembly. As the fasteners aredistally advanced, the legs of the fasteners are formed by the fastenerforming pockets 256 a defined in the anvil plate 250 to secure thebuttress material including the anvil buttress member 230 to the tissue.

Referring again to FIGS. 5-6, the knife 400 is simultaneously orthereafter advanced into the anvil assembly 200 to sever the clampedtissue and to advance into engagement with the proximal surface 272 a ofthe first annular member 270 of the ring assembly 260. Upon engagementwith the first annular member 270, the knife 400 distally drives theentire ring assembly 260 toward the anvil cap 220. Notably, as the ringassembly 260 is moved distally, the pair of opposed nubs 286 of thesecond annular member 280 slide through the channels 214 a of anvil head210 such that the ring assembly 260 drives the crush ring member 240distally into engagement with the one or more engaging features 224 ofthe anvil cap 220.

The distal movement of the crush ring member 240 into engagement withthe one or more engaging features 224 of the anvil cap 220 separates theproximal surface of the cap body 222 of the anvil cap 220 from thedistal surface of the head body 212 of the anvil head 210 so that theo-ring 215 separates from the extension portions 234 of the anvilbuttress member 230. In particular, the teeth 226 a of the snap features226 cam against the ramped partitions 218 so that each snap feature 226flexes radially outwardly into the opening 228 of the cap body 222 fromthe first recess 218 a of the head body 212 to enable the anvil cap 220to separate from the anvil head 210 as the anvil cap 220 moves from theapproximated position to the unapproximated position. After camming overthe ramped partitions 218, the teeth 226 a of the snap features 226 snapor flexes radially inwardly into the second recess 218 b of the headbody 212 to maintain the anvil cap 220 secured to the anvil head 210.The separation of the cap body 222 and the head body 212 creates a spaceor gap “G” between the proximal surface of the cap body 222 and a distalsurface of the head body 212 to free the extension portion 234 of theanvil buttress member 230 from between the anvil head 210 and the o-ring215 so that the anvil buttress member 230 is secured to the tissueindependent of the surgical stapling device 10.

As illustrated in FIG. 7, an embodiment of an anvil assembly isgenerally referred to as anvil assembly 500 and is substantially similarto anvil assembly 200 and thus, anvil assembly 500 is described hereinonly to the extent necessary to describe the differences in constructionand operation of the anvil assembly 500. Anvil assembly 500 includes acircular anvil head 210, an o-ring 215, an anvil cap 220, a circularanvil buttress member 230, a crush ring member 240, and an anvil plate250. Notably, anvil assembly 500 does not include ring assembly 260 andthus, when the circular knife 400 is advanced into the anvil assembly500 during operation, the blade of the circular knife 400 directlyengages the proximal surface of crush ring member 240 to drive the crushring member 240 distally into engagement with the anvil cap 220. Inparticular, as noted above, the distal movement of the crush ring member240 into engagement with the one or more engaging features 224 of theanvil cap 220 separates the proximal surface of the cap body 222 of theanvil cap 220 from the distal surface of the head body 212 of the anvilhead 210 so that the o-ring 215 separates from the extension portions234 of the anvil buttress member 230 to free the anvil buttress member230.

Although a manually operated handle assembly is shown in FIG. 1, in anyof the embodiments disclosed herein, the handle assembly can be poweredby a motor and an external or internal power source. One or more driveshafts extending through the elongate body can drive the variousfunctions (i.e., approximation, stapling and cutting) of the instrument.

In any of the embodiments disclosed herein, one or more of the crushring 240 and parts of the ring assembly 260 could be eliminated.Furthermore, the circular knife may directly move the anvil cap 220above to release the buttress member.

Persons skilled in the art will understand that the structures andmethods specifically described herein and illustrated in theaccompanying figures are non-limiting exemplary embodiments, and thatthe description, disclosure, and figures should be construed merely asexemplary of particular embodiments. It is to be understood, therefore,that the present disclosure is not limited to the precise embodimentsdescribed, and that various other changes and modifications may beeffected by one skilled in the art without departing from the scope orspirit of the disclosure. Additionally, it is envisioned that theelements and features illustrated or described in connection with oneexemplary embodiment may be combined with the elements and features ofanother without departing from the scope of the present disclosure, andthat such modifications and variations are also intended to be includedwithin the scope of the present disclosure. Indeed, any combination ofany of the presently disclosed elements and features is within the scopeof the present disclosure. Accordingly, the subject matter of thepresent disclosure is not to be limited by what has been particularlyshown and described.

What is claimed is:
 1. An anvil assembly comprising: an anvil head defining a first recess and a second recess, the first recess and the second recess separated by a ramped partition; a buttress member supported on the anvil head; an anvil cap movable relative to the anvil head between an approximated position and an unapproximated position, the anvil cap including a snap feature, the snap feature being positionable within the first recess when the anvil cap is disposed in the approximated position and being positionable within the second recess when the anvil cap is disposed in the unapproximated position, the snap feature configured to cam over the ramped feature as the anvil cap moves from the approximated position to the unapproximated position, the snap feature configured to flex outwardly from the first recess as the snap feature cams over the ramped partition and configured to flex inwardly into the second recess after camming over the ramped partition, the snap feature configured to maintain the anvil cap secured to the anvil head when the snap feature is disposed in the second recess; and a crush member movable into engagement with the anvil cap to move the anvil cap toward the unapproximated position so that the buttress member releases from the anvil head.
 2. The anvil assembly of claim 1, wherein the anvil cap supports an o-ring.
 3. The anvil assembly of claim 2, wherein the o-ring is formed of an elastomeric material.
 4. The anvil assembly of claim 2, wherein the o-ring is disposed in a compressed condition when the anvil cap is disposed in the approximated position, and wherein the o-ring is disposed in an uncompressed condition when the anvil cap is disposed in the unapproximated position.
 5. The anvil assembly of claim 2, wherein the buttress member includes a body portion and an extension portion that extends from the body portion.
 6. The anvil assembly of claim 2, wherein the anvil cap defines a groove configured to support the o-ring.
 7. The anvil assembly of claim 6, wherein the groove is defined in a bottom surface of the anvil cap.
 8. The anvil assembly of claim 5, wherein the extension portion includes at least one tab, the o-ring being compressed against the at least one tab when the anvil cap is disposed in the approximate position to maintain the body portion of the buttress member supported on a tissue engaging surface of the anvil head.
 9. A stapling device, comprising: a handle assembly; an elongate body that extends from the handle assembly; and an end effector mounted on a distal end of the elongate body and including a cartridge assembly and an anvil assembly, the anvil assembly including: an anvil head defining a first recess and a second recess separated by a ramped partition; a buttress member supported on the anvil head; an anvil cap movable relative to the anvil head between an approximated position and an unapproximated position, the anvil cap including a snap feature configured to cam over the ramped feature as the anvil cap moves from the approximated position to the unapproximated position, the snap feature configured to flex outwardly from the first recess as the snap feature cams over the ramped partition and configured to flex inwardly into the second recess after camming over the ramped partition, the snap feature configured to maintain the anvil cap secured to the anvil head when the snap feature is disposed in the second recess; and a crush member movable into engagement with the anvil cap to move the anvil cap toward the unapproximated position so that the buttress member releases from the anvil head.
 10. The stapling device of claim 9, wherein the anvil cap supports an o-ring.
 11. The stapling device of claim 10, wherein the o-ring is formed of an elastomeric material.
 12. The stapling device of claim 10, wherein the o-ring is disposed in a compressed condition when the anvil cap is disposed in the approximated position, and wherein the o-ring is disposed in an uncompressed condition when the anvil cap is disposed in the unapproximated position.
 13. The stapling device of claim 9, wherein the buttress member includes a body portion and an extension portion that extends from the body portion.
 14. The stapling device of claim 9, wherein, the snap feature is positionable within the first recess when the anvil cap is disposed in the approximated position and wherein the snap feature is positionable within the second recess when the anvil cap is disposed in the unapproximated position.
 15. The stapling device of claim 10, wherein the anvil cap defines a groove configured to support the o-ring.
 16. The stapling device of claim 15, wherein the groove is defined in a bottom surface of the anvil cap.
 17. A circular stapling device, comprising: a handle assembly; an elongate body that extends from the handle assembly; and an end effector mounted on a distal end of the elongate body and including a cartridge assembly and an anvil assembly, the anvil assembly including: an anvil head defining a first recess and a second recess separated by a ramped partition; a buttress member supported on the anvil head; an anvil cap movable relative to the anvil head between an approximated position and an unapproximated position, the anvil cap including a snap feature configured to cam over the ramped feature as the anvil cap moves from the approximated position to the unapproximated position, the snap feature configured to flex from the first recess as the snap feature cams over the ramped partition and into the second recess to maintain the anvil cap secured to the anvil head; and a crush ring movable into engagement with the anvil cap to move the anvil cap toward the unapproximated position so that the buttress member releases from the anvil head. 